I think this issue only occurs if you leave Magma Sprites for the end.
I want to share that this issue occurred for me as well. I am playing on a PS5. Stardew Valley | PS4 (version 1.57) with PS5 firmware up to date (version 21.01-03.10.00.03-00.00.00.0.1).
I was playing online co-op and was progressing through the adventurer guild kills. My multiplayer friends were not with me they were doing something else. I killed Pepper Rex to 50, received the notification that I protected the region from Pepper Rex at the bottom left of the screen. The notification popup is expected after completing an eradication goal. My last eradication was reach 150 Magma Sprites. I had about 100, and went to the Volcano dungeon to get the remaining 50 I had left. I went through 2 full days worth of Magma Sprites with monster musk, and did not receive a notification or a PSN Trophy Popup. I went to the adventurer's board and the game had marked it as completed.
I went to the Perfection Tracker in Qi's Cave and it says "Monster Slayer Hero: Yes".
On the Monster Eradication Goals signpost in the Adventurer Guild it says "215 Magma Sprites *"
The trophy never popped, and I never received the notification on the bottom left that I kept the area safe from Magma Sprites.
I also never received a letter with "Marlon's Phone Number" though someone in my multiplayer did a few weeks before me. They told me over voice chat that we can + now call Marlon over the phone to get our stuff back if we die in a mine.
Here are some google search results of other people with a similar problem:
Hi guys, Finally got around to completing all the Adventure Guild Monster Slayer Goals. No trophy popped. I've collected my rewards from Gil and double checked the list to make sure I'm not missing anything, but I've definitely got them all. Has anyone heard of this trophy glitching before? Is it...
forum.psnprofiles.com
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